UV Mapping a sculpted object shows glitches
Don't apply the subdivision modifier. This makes the geometry unnecessarily dense. Re-meshing may have solved your problem but this will not hold up.
Also smart UV unwrap isn't the best way to unwrap because of lack of control. Instead make creases and then unwrap using U&gt;Unwrap&gt;Unwrap. Also learn about edge-flow. This is very important when modelling.